The present invention relates to power tools and, more particularly, to small electric DC motors utilized in power tools with commutators and brushes formed from a titanium graphite material.
Power tools are utilized by professional tradesmen as well as weekend do-it-yourselfers. All power tools utilize electric motors which provide the desired output for the tool. Ordinarily, electric motors have a life expectancy around one hundred fifty (150) hours before the brushes and commutator require maintenance, replacement or repair.
Brushes which are currently used in electric motors are formed from a copper graphite material. These brushes ordinarily include thirty to forty (30-40%) percent of copper by weight and are satisfactory for their intended purpose. The copper commutators, likewise, are oxygen free high conductive copper with 10-25 ounces of silver per ton of copper in order to provide a reasonable motor life. Ordinarily, the commutator is designed so that it will withstand two sets of brushes before it is worn and requires replacement. While these commutators work satisfactorily for their intended purpose, designers are striving to improve both the brushes and the commutator wear life.
Accordingly, it is an object of the present invention to provide an electric motor which has an extended life. The electric motor within the power tool provides the art with brushes as well as a commutator which are manufactured from a titanium graphite material. Preferably, the titanium graphite material is a titanium silicon graphite which provides a self-lubricating effect while maintaining a long service life and outstanding electrical properties.
In accordance with a first aspect of the invention, an electric DC motor comprises a stator assembly and an armature rotatable within the stator assembly. A commutator is rotatable with the armature and is connected to the armature via a shaft. The commutator has an outer surface layer formed of a titanium graphite material. Brushes are associated with the commutator. The brushes are held in an end plate. The brushes are likewise formed from a titanium graphite material. The titanium graphite material includes titanium, silicon and graphite. Preferably, the material is Ti.sub.3 SiC.sub.2. Generally, the titanium graphite material is self-lubricating.
In accordance with a second embodiment of the invention, a power tool is provided with an electric motor. The electric motor includes a stator assembly and an armature rotatable within the stator assembly. A commutator is rotatable with the armature and is connected to the armature via a shaft. The commutator has an outer surface layer formed of a titanium graphite material. Brushes are associated with the commutator and are held by an end plate. The brushes are also formed from a titanium graphite material. The titanium graphite material includes titanium, silicon and graphite. The preferred material is Ti.sub.3 SiC.sub.2. The titanium graphite material is preferably self-lubricating.
Additional objects and advantages of the present invention will become apparent from the detailed description of the preferred embodiment, and the appended claims and accompanying drawings, or may be learned by practice of the invention.